854 research outputs found
High Density Preheating Effects on Q-ball Decays and MSSM Inflation
Non-perturbative preheating decay of post-inflationary condensates often
results in a high density, low momenta, non-thermal gas. In the case where the
non-perturbative classical evolution also leads to Q-balls, this effect shields
them from instant dissociation, and may radically change the thermal history of
the universe. For example, in a large class of inflationary scenarios,
motivated by the MSSM and its embedding in string theory, the reheat
temperature changes by a multiplicative factor of .Comment: 4 page
Inversion of the Diffraction Pattern from an Inhomogeneously Strained Crystal using an Iterative Algorithm
The displacement field in highly non uniformly strained crystals is obtained
by addition of constraints to an iterative phase retrieval algorithm. These
constraints include direct space density uniformity and also constraints to the
sign and derivatives of the different components of the displacement field.
This algorithm is applied to an experimental reciprocal space map measured
using high resolution X-ray diffraction from an array of silicon lines and the
obtained component of the displacement field is in very good agreement with the
one calculated using a finite element model.Comment: 5 pages, 4 figure
Fluxes and distribution of dissolved iron in the eastern (sub-) tropical North Atlantic Ocean
Aeolian dust transport from the Saharan/Sahel desert regions is considered the dominant external input of iron (Fe) to the surface waters of the eastern (sub-) tropical North Atlantic Ocean. To test this hypothesis, we investigated the sources of dissolved Fe (DFe) and quantified DFe fluxes to the surface ocean in this region. In winter 2008, surface water DFe concentrations varied between <0.1 nM and 0.37 nM, with an average of 0.13 ± 0.07 nM DFe (n = 194). A strong correlation between mixed layer averaged concentrations of dissolved aluminum (DAl), a proxy for dust input, and DFe indicated dust as a source of DFe to the surface ocean. The importance of Aeolian nutrient input was further confirmed by an increase of 0.1 nM DFe and 0.05 ?M phosphate during a repeat transect before and after a dust event. An exponential decrease of DFe with increasing distance from the African continent, suggested that continental shelf waters were a source of DFe to the northern part of our study area. Relatively high Fe:C ratios of up to 3 à 10?5 (C derived from apparent oxygen utilization (AOU)) indicated an external source of Fe to these African continental shelf waters. Below the wind mixed layer along 12°N, enhanced DFe concentrations (>1.5 nM) correlated positively with apparent oxygen utilization (AOU) and showed the importance of organic matter remineralization as an DFe source. As a consequence, vertical diffusive mixing formed an important Fe flux to the surface ocean in this region, even surpassing that of a major dust event
Non-local string theories on AdS_3 times S^3 and stable non-supersymmetric backgrounds
We exhibit a simple class of exactly marginal "double-trace" deformations of
two dimensional CFTs which have AdS_3 duals, in which the deformation is given
by a product of left and right-moving U(1) currents. In this special case the
deformation on AdS_3 is generated by a local boundary term in three dimensions,
which changes the physics also in the bulk via bulk-boundary propagators.
However, the deformation is non-local in six dimensions and on the string
worldsheet, like generic non-local string theories (NLSTs). Due to the
simplicity of the deformation we can explicitly make computations in the
non-local string theory and compare them to CFT computations, and we obtain
precise agreement. We discuss the effect of the deformation on closed strings
and on D-branes. The examples we analyze include a supersymmetry-breaking but
exactly marginal "double-trace" deformation, which is dual to a string theory
in which no destabilizing tadpoles are generated for moduli nonperturbatively
in all couplings, despite the absence of supersymmetry. We explain how this
cancellation works on the gravity side in string perturbation theory, and also
non-perturbatively at leading order in the deformation parameter. We also
discuss possible flat space limits of our construction.Comment: 40 pages, 6 figures, harvma
Study of EMIC wave excitation using direct ion measurements
With data from Van Allen Probes, we investigate electromagnetic ion cyclotron (EMIC) wave excitation using simultaneously observed ion distributions. Strong He band waves occurred while the spacecraft was moving through an enhanced density region. We extract from helium, oxygen, proton, and electron mass spectrometer measurement the velocity distributions of warm heavy ions as well as anisotropic energetic protons that drive wave growth through the ion cyclotron instability. Fitting the measured ion fluxes to multiple sinm-type distribution functions, we find that the observed ions make up about 15% of the total ions, but about 85% of them are still missing. By making legitimate estimates of the unseen cold (below âŒ2 eV) ion composition from cutoff frequencies suggested by the observed wave spectrum, a series of linear instability analyses and hybrid simulations are carried out. The simulated waves generally vary as predicted by linear theory. They are more sensitive to the cold O+ concentration than the cold He+ concentration. Increasing the cold O+ concentration weakens the He band waves but enhances the O band waves. Finally, the exact cold ion composition is suggested to be in a range when the simulated wave spectrum best matches the observed one
Measurement of one-particle correlations and momentum distributions for trapped 1D gases
van Hove's theory of scattering of probe particles by a macroscopic target is
generalized so as to relate the differential cross section for atomic ejection
via stimulated Raman transitions to one-particle momentum-time correlations and
momentum distributions of 1D trapped gases. This method is well suited to
probing the longitudinal momentum distributions of 1D gases in situ, and
examples are given for bosonic and fermionic atoms.Comment: 4 pages, 2 .eps figure
Perturbative and Nonperturbative Kolmogorov Turbulence in a Gluon Plasma
In numerical simulations of nonabelian plasma instabilities in the hard-loop
approximation, a turbulent spectrum has been observed that is characterized by
a phase-space density of particles with exponent , which is larger than expected from relativistic
scatterings. Using the approach of Zakharov, L'vov and Falkovich, we analyse
possible Kolmogorov coefficients for relativistic -particle
processes, which give at most perturbatively for an energy cascade.
We discuss nonperturbative scenarios which lead to larger values. As an extreme
limit we find the result generically in an inherently nonperturbative
effective field theory situation, which coincides with results obtained by
Berges et al.\ in large- scalar field theory. If we instead assume that
scaling behavior is determined by Schwinger-Dyson resummations such that the
different scaling of bare and dressed vertices matters, we find that
intermediate values are possible. We present one simple scenario which would
single out .Comment: published versio
A Fermi Surface Model for Large Supersymmetric AdS_5 Black Holes
We identify a large family of 1/16 BPS operators in N=4 SYM that
qualitatively reproduce the relations between charge, angular momentum and
entropy in regular supersymmetric AdS_5 black holes when the main contribution
to their masses is given by their angular momentum.Comment: 32 pages, 6 figures, LaTeX uses JHEP3 class; ver 2- added
acknowledgment, minor change
Are Three Additional Cycles of Chemotherapy Useful in Patients with Advanced-stage Epithelial Ovarian Cancer After a Complete Response to Six Cycles of Intravenous Adjuvant Paclitaxel and Carboplatin?â
BACKGROUND: To evaluate the efficacy of three additional cycles of chemotherapy in patients with the International Federation of Gynecology and Obstetrics Stage III or IV, who achieved a complete response after six cycles of intravenous adjuvant paclitaxel/carboplatin after surgery. METHODS: The clinical data of 94 patients with complete response after six cycles of adjuvant paclitaxel/carboplatin after surgery between January 1997 and March 2007 were reviewed retrospectively. Three additional cycles using the same chemotherapy were administered to 57 patients as consolidation chemotherapy (Group 1). Thirty-seven patients without the additional cycles served as controls (Group 2). Disease-free survival (DFS) and overall survival (OS) were evaluated using the Kaplan-Meier method with the log-rank test. The importance of consolidation chemotherapy as a prognostic factor affecting survival was examined using the Cox's proportional hazard analysis. The incidence of chemotherapy-induced hematological toxicities was compared between the two groups using chi-square test. RESULTS: Median DFS and mean OS were not significantly different between the two groups (15 versus 22 months, P = 0.703; 69 versus 73 months, P = 0.891, respectively). Consolidation chemotherapy was not a prognostic factor of survival although optimal debulking surgery and lower value of serum CA-125 levels after six cycles of the chemotherapy were prognostic factors improving DFS (P < 0.01). Grade 3 or 4 leukopenia was more common in patients treated with consolidation chemotherapy than in those not treated (50.9 versus 21.6%, P = 0.004). CONCLUSION: Consolidation chemotherapy using paclitaxel/carboplatin may be inefficient and relatively toxic to advanced-stage epithelial ovarian cancer patients with complete response to six cycles of the same chemotherapy after surgery
Turbulent Thermalization
We study, analytically and with lattice simulations, the decay of coherent
field oscillations and the subsequent thermalization of the resulting
stochastic classical wave-field. The problem of reheating of the Universe after
inflation constitutes our prime motivation and application of the results. We
identify three different stages of these processes. During the initial stage of
``parametric resonance'', only a small fraction of the initial inflaton energy
is transferred to fluctuations in the physically relevant case of sufficiently
large couplings. A major fraction is transfered in the prompt regime of driven
turbulence. The subsequent long stage of thermalization classifies as free
turbulence. During the turbulent stages, the evolution of particle distribution
functions is self-similar. We show that wave kinetic theory successfully
describes the late stages of our lattice calculation. Our analytical results
are general and give estimates of reheating time and temperature in terms of
coupling constants and initial inflaton amplitude.Comment: 27 pages, 13 figure
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